Two Common Species Recommended for Dormant Oil Treatments

Two Common Species Recommended for Dormant Oil Treatments

Coming up in in late winter/early spring, many of our Castle Rock clients schedule dormant oil treatment on their aspen or pine trees.

Given these are two key species in our area, dormant oil treatments are key in preventing needle scale on pine trees and oystershell scale on aspens.

Needle scale on pine trees

This scale is more easily controlled in early spring than any other time of the year.
Typically a dormant oil treatment is done in mild, late winter weather (40 to 60 degrees), because discoloration and staining can occur on nearby trees when temperatures are higher.

“Pine needle scale is an elongate, white insect that attaches itself to the needles of several pines, notably mugo,” according to CSU.

Premature or abnormally large needle drop on your pines, especially mugo pines, may indicate its presence.

Oystershell scale

Our staff sees this most commonly on aspens, but have also observed the telltale oystershell pattern on stems and branches of ash trees.  Oystershell scale is regarded as a tree killer, due to the aspens’ susceptibility to disease once the scale has sapped the tree’s vigor.

Dormant oil is also effective in preventing elm scale on elm trees

More common to our clients along the elm lined streets in Denver, elm scale will leave a sticky honeydew which drips down from the elm onto you and your neighbors’ parked cars and decks.